1. Field of the Invention
The invention concerns a saw blade for sawing ductile iron materials having a concrete lining, having a base element onto which a coating made of particles of hard material is applied. The invention also concerns a method for sawing pipes made of cast iron having a concrete lining.
2. Background
Pipes that supply water and carry off waste water are at present produced mostly from cast iron, and are additionally provided with a cement lining. To improve corrosion resistance, these pipes are often additionally coated on the outside with a layer of fiber-reinforced cement or concrete. The cast iron is generally cast iron with spheroidal graphite (GGG), in which carbon in the form of spheroidal graphite is enclosed in a basic structure that is usually predominantly ferrite or perlite.
Sawing such pipes, which usually possess a diameter on the order of from approximately 15 to approximately 40 cm and more, is highly problematical. Reciprocating saws are often used because of the confined conditions, especially when pipes are being laid or repaired in situ.
However, conventional saw blades coated with tungsten carbide have insufficient service life, and often become so deformed while cutting through a single pipe that it is no longer possible to continue working with the same blade.
Diamond-coated saw blades are also unsuitable, since they have a tendency to smear because of the graphite particles contained in the gray cast iron, so that cutting performance is insufficient and the saw blades quickly deform because of the high applied pressure required.
The sawing process is further complicated by the fact that in the repair of water pipes, small quantities of water continue to flow through the pipe despite complete shutoff of the water; this means that working conditions are wet, which causes caking of the cement at the cut.